Avaliação morfométrica aliada a análise temporal de uso e ocupação da terra de 5 microbacias hidrográficas contribuintes ao Rio Lajeado Pardo de Frederico Westphalen - RS

Abstract

Water availability in terms of quantity and quality, is one of the main concerns discussed currently. The watersheds and catchment areas are units of the natural division, composed of a drainage network and a main river, one of the most important sources of urban and rural water supply. The quality of this resource depends on the mutual and complex interaction of biophysical, social, economic, and demographic factors present in the area. Thus, considering the Lajeado Pardo River as one of the main sources of water supply of the Municipality of Frederico Westphalen - RS, sought to delimit five watersheds that supply and contribute to the Lajeado Pardo, their morphometric aspects, complementary to the temporal analysis of land use and cover, constitution of Permanent Preservation Areas (APP) and temporal monitoring of the largest forest fragments with vegetation indices. The analyses were performed using GIS tools, using images from the Landsat satellite, MAPBIOMAS project, and Topodata. The morphometric data combined with the result of temporal analysis of land use and occupation showed the greatest fragility of watershed 1, which obtained a high tendency to flood occurrences and the highest average slope, being the only one to present total forest area loss, containing in 2021, only 16.2% composed of it. The data showed significant occupation of agricultural planting classes and urban areas in the other units. The APP area (30m) demonstrated the fragility of water courses and non-compliance with the Law in all units, with the most alarming value in microbasin 3, with only 38.6% of correct composition. The analysis of the largest forest fragments identified greater variations in the average NDVI in fragment E, located on the urban margin.